The present invention relates generally to carbon dioxide turbines. In particular, the invention relates to carbon dioxide turbines powered by a renewable energy source.
There is a continuing demand for clean renewable energy sources due to the depletion of the Earth's supply of fossil fuels and concerns over the contribution to global warming from combustion of fossil fuels. Solar power towers generate electric power from sunlight by focusing concentrated solar radiation on a tower-mounted receiver. Solar power tower systems typically include a “cold” storage tank, a solar receiver, heliostats, a “hot” storage tank, and an energy conversion system, such as a steam generator and turbine/generator set. In operation, a heat transfer fluid is pumped from the cold storage tank to the solar receiver. The heat transfer fluid can be any appropriate medium that has the capability to transfer heat and thermally maintain the heat in the medium, such as water, liquid metal, or molten salt.
The solar receiver is typically positioned 50 feet to 250 feet or more above ground and is heated by the heliostats. The heliostats redirect and concentrate solar radiation from the sun onto the solar receiver. The heat transfer fluid flows through receiver tubes of the solar receiver where it is heated by the concentrated solar energy. In the solar receiver, liquid metals have been used as the heat transfer fluid and can reach temperatures of approximately 1600 degrees Fahrenheit (° F.). Water/steam being used as the heat transfer fluid can reach peak temperatures of approximately 1050° F. Molten salts currently being used as the heat transfer fluid can reach temperatures of approximately 1100° F.
After the heat transfer fluid has been heated in the solar receiver, the heat transfer fluid typically flows into the hot thermal storage tank. The heat transfer fluid is then stored in the hot thermal storage tank until it is needed for electrical power generation. The hot thermal storage tank allows for electrical power production during cloudiness or darkness. When electrical energy is needed, the hot heat transfer fluid is pumped from the hot storage tank to an energy conversion system. The heat transfer fluid transfers the heat within the energy conversion system. The energy conversion system can be, for example, a Rankine cycle conversion system or a Brayton cycle conversion system. Brayton cycles, with the use of a regenerator (also called a recuperator) typically have higher efficiencies than Rankine cycles, which have efficiencies of approximately 34% to 40%. After the heat has been removed from the heat transfer fluid, the heat transfer fluid is transported back to the cold storage tank for reuse.
Due to the concern of depleting natural resources and the effect of pollution on global warming, there is a need in the art for a method of producing electricity using renewable resources. In addition, solar power facilities typically have high capital costs, thus, there is also a need in the art for a method of producing electricity in an efficient and cost-effective manner.